It is a common misunderstanding that human babies possess the ability to breathe underwater immediately following birth. While newborns develop within a fluid-filled environment in the womb, their respiratory system is specifically structured for air breathing once they enter the external world. They do not have gills or the physiological adaptations necessary to extract oxygen from water.
The First Breath
A profound physiological transformation occurs within a newborn’s body at birth, enabling the crucial first breath. Prior to birth, the fetus receives all its oxygen and nutrients through the placenta and umbilical cord, bypassing the fluid-filled lungs.
When the umbilical cord is clamped and the baby is exposed to the cooler, air-filled environment outside the womb, rapid changes begin. This environmental shift triggers the infant’s central nervous system, prompting the first gasp of air, typically within 10 seconds. The lungs, previously collapsed, inflate as the baby generates negative pressure to draw in air.
This expansion decreases resistance to blood flow in the pulmonary arteries, allowing blood to circulate through the lungs for oxygenation. Simultaneously, fetal circulatory shunts like the foramen ovale and ductus arteriosus begin to close, redirecting blood flow to establish an adult-like pattern where lungs are fully engaged in gas exchange.
The Infant Diving Reflex
Newborns exhibit an innate physiological response known as the infant diving reflex, or bradycardic reflex, which can be observed from birth until approximately six months of age. This reflex triggers when a baby’s face, especially nostrils and mouth, is immersed in water. The response involves automatic adjustments: breath-holding (apnea), slowed heart rate (bradycardia), and redirected blood flow from extremities to the brain and heart. This protective mechanism conserves oxygen and prevents water from entering the lungs by sealing the glottis. However, it does not enable a baby to breathe underwater; it is a survival response for short submersion periods, prioritizing oxygen supply to vital organs. The reflex is not foolproof and cannot sustain life indefinitely.
Understanding Water Birth
Water birth is a practice where a mother labors and/or delivers her baby in a tub of warm water. This method is considered safe because specific physiological mechanisms prevent the newborn from inhaling water. During a water birth, the baby remains in a fluid environment, similar in temperature and pressure to the womb, until their head is fully delivered and exposed to air. The baby’s first breath is not stimulated until their face makes contact with the cooler air, triggering the respiratory drive. While submerged, the umbilical cord provides oxygenated blood, preventing the need to breathe, and the infant diving reflex causes breath-holding and swallowing of any water, rather than inhalation.
Risks of Submerging Infants
Intentionally submerging an infant’s face or body in water with the expectation they can breathe presents significant hazards, as the temporary diving reflex does not confer the ability to breathe water, making accidental drowning a serious risk. Drowning is a leading cause of unintentional death in young children, and babies can drown in as little as a few inches of water. Beyond drowning, hypothermia is a danger, particularly if the water is cold, as infants have less body fat to insulate them and struggle with temperature regulation. Water intoxication is another concern, where excessive water intake can dilute a baby’s sodium levels, potentially leading to seizures, brain damage, or coma. These risks underscore that babies are air-breathing organisms from birth and require careful supervision around any body of water.